What is Proof: Definition and 999 Discussions

A mathematical proof is an inferential argument for a mathematical statement, showing that the stated assumptions logically guarantee the conclusion. The argument may use other previously established statements, such as theorems; but every proof can, in principle, be constructed using only certain basic or original assumptions known as axioms, along with the accepted rules of inference. Proofs are examples of exhaustive deductive reasoning which establish logical certainty, to be distinguished from empirical arguments or non-exhaustive inductive reasoning which establish "reasonable expectation". Presenting many cases in which the statement holds is not enough for a proof, which must demonstrate that the statement is true in all possible cases. An unproven proposition that is believed to be true is known as a conjecture, or a hypothesis if frequently used as an assumption for further mathematical work.Proofs employ logic expressed in mathematical symbols, along with natural language which usually admits some ambiguity. In most mathematical literature, proofs are written in terms of rigorous informal logic. Purely formal proofs, written fully in symbolic language without the involvement of natural language, are considered in proof theory. The distinction between formal and informal proofs has led to much examination of current and historical mathematical practice, quasi-empiricism in mathematics, and so-called folk mathematics, oral traditions in the mainstream mathematical community or in other cultures. The philosophy of mathematics is concerned with the role of language and logic in proofs, and mathematics as a language.

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  1. B

    Proof that disk of charge = point charge when very far?

    Homework Statement Take the expression 21.11 (pictured below, specifically the bottom one) for the electric field above the center of a uniformly charged disk with radius R and surface charge density σ, and show that when one is very far from the disk, the field decreases with the same square...
  2. E

    Calculus Taylor Approximation Proof

    1. The question is. Show that if |nx| <1, the following is exact up to (and including) the x^2 order. The hint giving says to use the Taylor Expansion for both sides of the equation2. (1+x)^n = e^n(x-(1/2)x^2) ; the n(x-(1/2)x^2) is all an exponent3. My first attempt was to take the taylor...
  3. little neutrino

    Proof for Lorentz Transformation of Momentum: Step Explained

    Hi. In the attached proof for Lorentz transformation for momentum http://www.colorado.edu/physics/phys2170/phys2170_sp07/downloads/lorentz_transformation_E_p.pdf, there is this step that I don't understand: 1/√1-u'2/c2 = γ(1-vux/c2)/√1-u2/c2 Can someone explain how they derived this? Thanks! :)
  4. RJLiberator

    [Abstract Algebra] GCD and Relatively Prime Proof

    Homework Statement If gcd(f(x),g(x)) = 1 and m,n ∈ ℕ, show that gcd(f(x)^m, g(x)^n) = 1. Homework EquationsThe Attempt at a Solution So I had previously proved this for non-polynomials: gcd(a,b)=1 then gcd(a^n,b^n)=1 Proof: a = p1*p2*...*pn b = p1*p2*...*pm then a^n = p1^n*p2^n*...*pn^n...
  5. TeethWhitener

    Question about proof from Bishop & Goldberg

    I'm going through Bishop and Goldberg's "Tensor Analysis on Manifolds" right now and I'm stuck in Chapter 0. :H They give a proof of the statement "A compact subset of a Hausdorff space is closed" that I can't seem to wrap my head around. I'm reprinting the proof here: "Suppose that A is a...
  6. TheMathNoob

    What is Z_2^n and its role in proving the vertices of a hypercube in R^n?

    Homework Statement Attached is the problem. I didn't find anyway to apply the hamming distance to this problem, but I hope that at least this is close to show something. Homework EquationsThe Attempt at a Solution Lets consider Rn over Z 2 n, so the basis of R n under Z 2 is (0,0,………0 )all the...
  7. P

    Linear algebra : Doing a proof with a square matrix

    Homework Statement Show that all square matrix (A whatever) can be written as the sum of a symmetric matrix and a anti symmetric matrix. Homework Equations I think this relation might be relevant : $$ A=\frac{1}{2}*(A+A^{T})+\frac{1}{2}*(A-A^{T}) $$ The Attempt at a Solution I know that we...
  8. Comeback City

    Mathematical Proof that Photons have No Rest Mass

    Using these equations I am about to prove that photons have a rest mass of zero (mathematically) ________________________________________________________________________________________ E=hc/λ Photon Energy Equation E2=(pc+mc2)2 Mass-Energy Equivalence with Momentum Equation p=h/λ Momentum...
  9. A. Neumaier

    Are tracks in collision experiments proof of particles?

    I'd like to discuss the question in the title, following up on my remark quoted below. Note that I don't want to repeat the discussion in https://www.physicsforums.com/threads/tracks-in-particle-detectors-and-quantum-paths.758778 so maybe reread that one first! The traditional analysis is...
  10. RJLiberator

    Integral Domain, r^2 = r proof that r = 0 or 1

    Homework Statement Let r be an element of an integral domain R such that r^2 = r. Show that either r = 0_R or 1_R Homework Equations integral domain means no zero divisors. The Attempt at a Solution This is fundamental as 0 and 1 solve r^2 = r and are the only solutions. However, I'm not...
  11. RJLiberator

    Simple Abstract Algebra Proof: T(0_r) = 0_s

    Homework Statement Let T:R-> S be a homomorphism of rings. Show that T(0_r) = 0_s. Homework EquationsThe Attempt at a Solution First off, the terminology used is kinda confusing. I take 0_r to be the zero in R. Is this correct? For some reason I recall my teacher quickly saying that it was...
  12. C

    Clarification: proof that perfect subsets of R^k uncountable

    From Baby Rudin "Thm: Let P be a non-empty, perfect subset of R^k. Then P is uncountable. Pf: Since P has limit points, P must be infinite. Suppose P is countable, list the point of P {x1 ...xn }. Construct a sequence of nbhds. as follows. Let V1 be any nbhd of x1 . Suppose Vn has been...
  13. P

    Proof involving group of permutations of {1,2,3,4}.

    Homework Statement Let ##\sigma_4## denote the group of permutations of ##\{1,2,3,4\}## and consider the following elements in ##\sigma_4##: ##x=\bigg(\begin{matrix}1&&2&&3&&4\\2&&1&&4&&3\end{matrix}\bigg);~~~~~~~~~y=\bigg(\begin{matrix}1&&2&&3&&4\\3&&4&&1&&2\end{matrix}\bigg)##...
  14. C

    Proof: integral of continuous function is 0 so function is 0

    I've just encountered this somewhere and I need some sort of formal proof for why a continuous function ##f(x)## can equal zero because its integral is zero. Are there any out there? I've seen similar forum posts on places like Stack Exchange and one here, but I can't exactly follow the logic...
  15. Math Amateur

    MHB Vector Spaces .... Linear Dependence and Indepence .... Basic Proof Required

    In Andrew McInerney's book: First Steps in Differential Geometry, Theorem 2.4.3 reads as follows:https://www.physicsforums.com/attachments/5252McInerney leaves the proofs for the Theorem to the reader ... I am having trouble formulating a proof for Part (3) of the theorem ... Can someone help...
  16. UncertaintyAjay

    Proof Practice Ideas: Books, Exercises, & Theorems

    Could anyone recommend some books or exercises to practice proofs? Or even post some theorems to prove? Thanks in advance, Ajay
  17. Kingyou123

    Induction Proof Help: Understanding Equations for Homework | Prof. Note's Tips

    Homework Statement Homework Equations Prof. Note's. The Attempt at a Solution I'm on the 3 line where my Prof. combines both equations, I'm confused on what my equation should look. Her's was (n+1)(n+1)+1)/2
  18. RJLiberator

    Abstract Algebra: Another Ring Proof

    Homework Statement Let R be a ring and suppose r ∈R such that r^2 = 0. Show that (1+r) has a multiplicative inverse in R. Homework Equations A multiplicative inverse if (1+r)*x = 1 where x is some element in R. The Attempt at a Solution We know we have to use two facts. 1. Multiplicative...
  19. RJLiberator

    Abstract Algebra: Ring Proof (Multiplicative Inverse)

    Homework Statement Suppose R is a commutative ring with only a finite number of elements and no zero divisors. Show that R is a field. Homework Equations Unit is an element in R which has a multiplicative inverse. If s∈R with r*s = 1. A zero divisor is an element r∈R such that there exists...
  20. M

    Proof of Invertibility: Linear Map's Surjectivity and Injectivity Condition

    I am trying to understand the following basic proposition about invertibility: a linear map is invertible if and only if it is injective and surjective. Now suppose ##T## is a linear map ##T:V\rightarrow W##. The book I read goes the following way in proving the proposition in the direction when...
  21. sciencejournalist00

    Is this mathematical proof that beamsplitters entangle photons

    Prof. S Lakshmi Bala from Department of Physics, Madras, India writes a blackboard of equations which show how beamsplitters used alone affect the wavefunctions of input photons. It seems that it depends on the number of photons you use and in which input port to get you a different entangled...
  22. G

    Foundations Intro to Proof (Foundational) Mathematics

    Hello, I'm trying to self teach myself Fundamental Mathematics. I looked around, but I wasn't sure what to look for exactly. I read the part on Set Theory in "Book of Proof" by Richard Hammack. I enjoyed it, but I wasn't sure if it is rigorous enough to stand against a college level course...
  23. K

    Proof involving partitions and equivalence class

    Homework Statement Show that every partition of X naturally determines an equivalence relation whose equivalence classes match the subsets from the partition. Homework Equations ( 1 ) we know that equivalence sets on X can either be disjoint or equal The Attempt at a Solution Let Ai be a...
  24. M

    MHB Proof of Gρ(x)=ρGxρ−1 in Symmetric Groups

    Let G be a subgroup of Sym(X) and ρ ∈ G. Prove that Gρ(x) = ρGxρ−1, where ρGxρ−1 = {ρgρ−1|g ∈ Gx} What I Know: I need to somehow prove the left is contained in the right and the right is contained in the left. What I Have Done: Well based on the definition of a stabilizer Gx I assumed that...
  25. DocZaius

    Proof for {lim of exp = exp of lim}

    I don't know how to Google appropriately for this, since the kind of keywords I use present me with search results that try to define the exponential function using limits instead of what I am trying to ask: What does the proof look like for the following (assuming f(x) is "nice"). Any sites...
  26. T

    Proof that log2(i) is rational but I think it is wrong

    m and n are integers. log2(i) = m/n 2^(m/n) = i 2^m = i^n 2^0 = i^4 = 1 so that means that log2(i) is rational because there are integers n and m so that log2(i) = m/n , they are m=0 and n=4. But what I do get about this proof is that it seems to imply that log2(i) = 0/4 = 0 while google says...
  27. Alex_Doge

    Proof that an interval is a confidence interval for Geom(q)

    Hello Physicsforum Homework Statement I have a problem proving this: Given C(x)=[0, 3/x] for all x\in\chi, with \chi=\Omega being the sample space and P_q=Geom(q) being the geometric distribution. I have to show that C(x) is a confidence Interval for q but I don't know how to get started...
  28. W

    Proof that the world is not flat

    I'm reading the book by Zee, I came across a paragraph saying that the world is not flat. "Given an airline table of distances, you can deduce that the world is curved without ever going outside. If I tell you the three distances between Paris, Berlin, and Barcelona, you can draw a triangle on...
  29. F

    Quantum Which books say about general proof of renormalization?

    Which books in QFT give representations about general proof of renormalization?I know that the book of QFT of Peskin&Schroder does not give the full demontration.
  30. P

    Is this proof of an ##\infty## norm valid?

    I am trying to prove ##||A||_{\infty} = max_i \sum_{j} |a_{ij}|## which reads as the ##\infty## norm is the max row sum of matrix A. ##i## is the row index and ##j## is the column index. Here is what I thought of: ##||A||_{\infty} = sup_{x\neq 0} \frac{||Ax||_{\infty}}{||x||_{\infty}}## The...
  31. S

    Proving Lorentz Transform Without Light Signal

    The thought experiment used to prove Lorentz transform uses a light signal as an assumption. What if there was something other than the light signal then Lorentz transformation would have totally different term in place of 'c'(speed of light).
  32. A

    Proof that COF depends only on asperities

    Homework Statement I am trying to craft a hypothesis regarding factors that affect the coefficient of friction. I know that it is determined by the triboforces and asperity interactions at the interface between the materials (among other factors, but right now I'm just going to focus on this)...
  33. C

    Proof about successor function

    Homework Statement Successor of a set x is defined as S(x)=x \cup {x} Prove that if S(x)=S(y) then x=y Our teacher gives us a hint and says use the foundation axiom. The Attempt at a Solution if S(x)=S(y)=x \cup {x}=y \cup {y} I feel like doing a proof by contradiction would work...
  34. RJLiberator

    Relatively prime proof involving a^n and b^n

    Homework Statement Show that if a, b, n, m are Natural Numbers such that a and b are relatively prime, then a^n and b^n are relatively prime. Homework Equations Relatively prime means 1 = am + bn where a and b are relatively prime. gcd(a,b) = 1 We have a couple corollaries that may be...
  35. G

    Mean value theorem variation proof

    Homework Statement Let f is differentiable function on [0,1] and f^{'}(0)=1,f^{'}(1)=0. Prove that \exists c\in(0,1) : f^{'}(c)=f(c). Homework Equations -Mean Value Theorem The Attempt at a Solution The given statement is not true. Counter-example is f(x)=\frac{2}{\pi}\sin\frac{\pi}{2}x+10...
  36. AutumnWater

    Epsilon Delta proof of a 2variable limit. Is my proof valid?

    Homework Statement Use the epsilon delta definition to show that lim(x,y) -> (0,0) (x*y^3)/(x^2 + 2y^2) = 0 Homework Equations sqrt(x^2) = |x| <= sqrt(x^2+y^2) ==> |x|/sqrt(x^2+y^2) <= 1 ==> |x|/(x^2+2y^2)? The Attempt at a Solution This limit is true IFF for all values of epsilon > 0, there...
  37. TheMathNoob

    Graph theory proof (Unlabeled trees)

    Homework Statement A. Show that n^n−2/n! < T(n) by looking at how the symmetric group Sn acts on labelled trees. Use |Sn| = n! T(n) is the number of unlabeled trees on n vertices Homework EquationsThe Attempt at a Solution I can't find any mathematical relation between labelled trees and...
  38. I

    Proof that e is irrational using Taylor series

    Homework Statement Using the equality ##e = \sum_{k=0}^n \frac{1}{k!} + e^\theta \frac{1}{(n+1)!}## with ##0< \theta < 1##, show the inequality ##0 < n!e-a_n<\frac{e}{n+1}## where ##a_n## is a natural number. Use this to show that ##e## is irrational. (Hint: set ##e=p/q## and ##n=q##)...
  39. T

    Understanding proof for Heisenberg uncertainty

    I've uploaded a proof of the Heisenberg uncertainty principle from Konishi's QM. I just don't quite understand one part: what is the significance of the discriminant being less than or equal to 0? Wouldn't this just result in ## \alpha = R \pm iZ ##? Why would this be desired in this proof?
  40. RJLiberator

    Proof: There Exists a prime p such that p=< sqrt(n)

    Homework Statement Question: Let n> 1 be an integer which is not prime. Prove that there exists a prime p such that p|n and p≤ sqrt(n). Homework Equations Fundamental theorem of arithmetic: Every integer n >1 can be written uniquely (up to order) as a product of primes. The Attempt at a...
  41. TheMathNoob

    Proving a Cycle Exists in Finite Graphs with Degree 2+ Vertices

    Homework Statement Exercise 0.1. Suppose that G is a finite graph all of whose vertices has degree two or greater. Prove that a cycle passes through each vertex. Conclude that G cannot be a tree. Homework EquationsThe Attempt at a Solution If every vertex in a graph G has degree two or...
  42. TheMathNoob

    Proving a Tree is a Minimally Connected Graph in Graph Theory

    Homework Statement Let G be a connected graph. We say that G is minimally connected if the removal of any edge of G (without deleting any vertices) results in a disconnected graph. (a) Show that a connected, minimally connected graph has no cycles. (b) Show that a connected graph with no cycles...
  43. H

    Proof of the Rodrigues formula for the Legendre polynomials

    How is the below expression for ##a_{n-2k}## motivated? I verified that the expression for ##a_{n-2k}## satisfies the recurrence relation by using ##j=n-2k## and ##j+2=n-2(k-1)## (and hence a similar expression for ##a_{n-2(k-1)}##), but I don't understand how it is being motivated. Source...
  44. P

    MHB Help with Non-Triangle Proof Needed

    can someone help me with another proof? it isn a triangle proof but this is the closest forum chat i could find
  45. Alpharup

    Uniqueness of limit proof

    Spivak proves that limit of function f (x) as x approaches a is always unique. ie...If lim f (x) =l x-> a and lim f (x) =m x-> a Then l=m. This definition means that limit of function can't approach two different values. He takes definition of both the limits. He...
  46. TheMathNoob

    Does Induction Work for Proving Graph Theory Statements?

    Homework Statement Prove that a complete graph with n vertices contains n(n − 1)/2 edges. Homework EquationsThe Attempt at a Solution The solution gives and inductive proof, but I am just wondering if this works as well. If we have a set of n vertices or points and we try to match all...
  47. TheMathNoob

    Proof about isomorphism (Graph Theory)

    Homework Statement 1. Prove or disprove up to isomorphism, there is only one 2-regular graph on 5 vertices. Homework EquationsThe Attempt at a Solution I am making this thread again hence I think I will get more help in this section old thread...
  48. TheMathNoob

    Proof about isomorphism (Graph Theory)

    Homework Statement 1. up to isomorphism, there is only one 2-regular graph on 5 vertices. Homework EquationsThe Attempt at a Solution I am still working on the problem, but I don't understand what up to isomorphism means. Does it mean without considering isomorphism?. I just need help with...
  49. R

    Vibration proof hinge and lock

    Hi All. I am stuck in a problem. Please check the image attached. It's part of a foldable mechanism of a quad copter arm. The red part is fixed to the body, the grey part is fixed to arms. The transparent part is a threaded collar/sleeve. The yellow part is a stopper. The hinge is a connecting...
  50. T

    Proving an equality using induction proof not working

    Homework Statement I work out the problem completely and it does not equal out. Having problems with two variable induction proofs (n and k) in this problem. Below is as far as I got, jpeg below Homework EquationsThe Attempt at a Solution
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